May, 1909.] 
The Catalpa Leaf Spot. 
511 
the spores were viable. The stress of other duties prevented a 
repetition of the experiment and the negative results here secured, 
throw but little light upon the source of infection. 
In addition to the fungi already mentioned as occurring upon 
the leaf spots of the catalpa, the writer found a species of Epi- 
coceum flourishing upon every spot in the leaves collected at 
Columbus as well as upon every spot examined in the material 
taken from the herbarium though it was not abundant upon that 
labelled Phyllosticta catalpae. There is also present on the spots 
in the leaves collected at Columbus and on those in herbarium 
specimens labeled Macrosporium catalpae a species of Cladospor- 
ium, a fungus that, so far as the writer is aware, has not been 
reported for the catalpa. These two fungi, however, are in all 
probability soprophytes that have no part in producing the 
spots upon the leaves. The results of this investigation tend to 
show that the species of Alternaria ( = Macrosporium) occurring 
on the catalpa is likewise a saprophytic form. Therefore, in 
summing up the work so far as it has been carried the writer is 
of the opinion that the disease-producing species is Didymos- 
pheria catalpae , of which Phyllosticta catalpae is an imperfect form 
and that the other species of fungi found upon the leaf spots are 
saprophytic. Whether or not this is the true relationship exist¬ 
ing among these different species of fungi remains still to be 
proved—a task the writer hopes to find at some future time 
opportunity to perform. 
EXPLANATION OF PLATE XXVI. 
The drawings were made with a Spencer microscope equipped 
with a 3 mm. objective and an 8 x ocular (4 x ocular used with 
No. 6). All are camera drawings made at table distance; 
reduced one-half in reproductions. The magnification in the 
microphotographs was not computed. 
Fig. 1. Conidial spores of Alternaria sp. on leaves collected at 
Columbus. 
Fig. 2. Conidial spores from herbarium specimen labeled Macro¬ 
sporium catalpae. 
Fig. 3. Conidial spores from herbarium specimen labeled Phyllos¬ 
ticta catalpae. 
Fig. 4. Conidiophores and conidia developed by placing in water 
spots taken from leaves collected at Columbus. The number of spores in 
the chains varied from 5 to 8. 
Fig. 5. Chain of spores found on herbarium specimen labeled 
Macrosporium catalpae. 
Fig. 6. Ascus of Didymosphaeria catalpae drawn from a stained 
section. 
Fig. 7. Ascospores of Didymosphaeria catalpae drawn from stained 
material. 
Fig. 8. Microphotograph of a perithecium in a leaf spot. 
Fig. 9. Microphotograph of a section of a leaf spot showing a 
perithecium of Diaymosphaerium catalpae at (a) and a pycnidium of Phyl¬ 
losticta catalpae at ( b). 
Fig. 10. Microphotograph of section of perithecium from which 
Figure 6 was drawn. 
